Let A, 1 < i < 5, be the domains for a table D ⊂ A1 × A2 × A3 × A4 × A5, where A1 = {1,2} (used to identify the daily vitamin capsule produced by two pharmaceutical companies), A2 = {A, D, E}, and A3 = A4 = A5 = Z+. The table D is given as Table 5.8.
(a) What is the degree of the table?
(b) What is the projection of D on A1 × A2? on A3 × A4 x A5?
c) This table has no primary key. (See Exercise 13.) We can, however, define a composite primary key as the cross product of a minimal number of domains of the table, whose components, taken collectively, uniquely identify each list of D. Determine some composite primary keys for this table.